115 lines
3.6 KiB
Racket
115 lines
3.6 KiB
Racket
#lang racket
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;; (C) Copyright Collin J. Doering 2014
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;;
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;; This program is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;;
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;; This program is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;;
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;; You should have received a copy of the GNU General Public License
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;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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;; File: DFA.rkt
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;; Author: Collin J. Doering <collin.doering@rekahsoft.ca>
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;; Date: Aug 27, 2014
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;; Description: an implementation of Determinalistic Finite Autamata
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(require (for-syntax syntax/parse))
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;; Some structures to represent a DFA
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(struct dfaState (trans))
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(struct dfaEndState dfaState ())
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(struct dfaStartState dfaState ())
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(struct dfaStartEndState dfaState ())
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(struct dfa (alpha start states))
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(define (compute-dfa m xs)
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(define/match (run-dfa state ys)
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[((or (dfaEndState _)
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(dfaStartEndState _)) '()) 'accept]
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[(_ '()) 'reject]
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[((dfaState f) (cons z zs)) (run-dfa (f z) zs)])
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(run-dfa (dfa-start m) xs))
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(define-syntax (define-dfa stx)
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(define-syntax-class transition
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#:description "dfa state transition"
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(pattern (in (~optional ->) out:id)))
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(define-syntax-class state
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#:description "dfa state"
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(pattern (name:id (~optional (~seq (~and #:end end?))) trans:transition ...+)
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#:with (in ...) #'(trans.in ...)
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#:with (out ...) #'(trans.out ...)))
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;; (pattern (name:id (~seq (~and #:end end2?)) (~optional (~and #:end end?))))
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(syntax-parse stx
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[(_ name:id alpha:expr start:state rests:state ...)
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#:fail-when (check-duplicate-identifier
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(syntax->list
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#'(start.name rests.name ...)))
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"duplicate state names"
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#'(define name
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(letrec ([start.name
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(dfaStartState
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(match-lambda [start.in start.out] ...))]
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[rests.name
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(dfaState
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(match-lambda [rests.in rests.out] ...))] ...)
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(dfa 'alpha start.name '(start.name rests.name ...))))]))
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;; ----------------------------------------------------------------------------
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(define-dfa odd-binary (0 1)
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[s0 (0 -> s0)
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(1 -> s1)]
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[s1 (0 -> s0)
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(1 -> s1)]
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[s2 #:end
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(0 -> s2)
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(1 -> s1)]
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[s3 #:dead (0 -> s3) (1 -> s3)])
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;; Odd binary dfa expansion
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(define odd-dfa
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(letrec ([s0 (dfaStartState (match-lambda [0 s0]
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[1 s1]))]
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[s1 (dfaEndState (match-lambda [0 s0]
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[1 s1]))])
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(dfa '(0 1) s0 '(s0 s1))))
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;; Even binary dfa expansion
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(define even-dfa
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(letrec ([s0 (dfaStartState (match-lambda [0 s0]
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[1 s1]))]
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[s1 (dfaState (match-lambda [0 s2]
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[1 s1]))]
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[s2 (dfaEndState (match-lambda [0 s0]
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[1 s1]))])
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(dfa '(0 1) s0 '(s0 s1 s2))))
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;; Odd binary dfa macro
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;; (define-dfa odd-dfa (0 1)
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;; [s0 (0 -> s0)
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;; (1 -> s1)]
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;; [s1 end
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;; (0 -> s0)
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;; (1 -> s1)])
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;; ;; Even binary dfa macro
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;; (define-dfa even-dfa (0 1)
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;; [s0 (0 -> s0)
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;; (1 -> s1)]
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;; [s1 (0 -> s2)
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;; (1 -> s1)]
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;; [s2 end
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;; (0 -> s0)
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;; (1 -> s1)])
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